Electron gun structure and method



R. M. BOWIE Re'. 22,378

ELECTRON GUN STRUCTURE AND METHOD OF ASSEMBLY THEREOF Sept. 21, 1943.

Original Filed Aug. 26, 1937 2 Sheets-Sheet 1 INVENTOR R. M. BOWIE Sept. 21, 1943.

ELECTRON GUN STRUCTURE AND METHOD OF ASSEMBLY THEREOF Original Filed. Aug. 26, 1937 2 Sheets-Sheet 2 KM 71PM v INVENTOR BY W Z A TTol qEY I I J Reissued Sept. 21, 1943 ELECTRON GUN STRUCTURE AND METHOD F ASSEMBLY THEREOF Robert M. Bowie, Emporium, Pa; assignor to SylvaniaElectric Products,- Inc., a corporation of Massachusetts Original No. 2,174,853, dated October 3, 1939, Se-

rial No. 160,981, August 26, 1937. Application for reissue March 14, 1940, Serial No. 324,014

2 ear s (01. 25.0-27.5).

This invention relates to electron guns and more particularly to electron guns of the type used in such devices as cathode-ray tubes, television tubes, oscilloscopes and the like.

A principal object of the invention is to provide an economical and highly accurate method of assembling and uniting the parts of an electron gun in rigid predetermined alignment and in insulated spaced relation. v

Heretofore in the assembly of electron guns for cathode-ray tubes and the like, it has been proposed to space the parts of the gun from one another by discs or rings of ceramic which were cut, molded or otherwise formed in their final rigid shape prior to assembly of the gun parts thereon. By this prior arrangement it is very essential that all parts be very accurately made in order that the axial symmetry and alignment of the gun shall be maintained. This has rendered necessary the use of expensive ceramic materials and expensive machining and grinding operations. I have found that when this prior method of assembly is employed with inexpensive ceramic materials, the finished gun is apt to exhibit axial misalignment. 1

Accordingly, it is an object of this inventio to provide a gun assembly method and structure which combine the accuracy of the usual expensive ceramic spacer constructions, while employing inexpensive materials for'rigidly spacing the parts, thus avoiding the necessity of grinding and accurate machining of the spacers and cooperating parts of the electrodes.

tion of the following detailed description and the appended claims. I

In general, according to the invention, the metal parts of the gun are first assembled in fixed aligned relationship in a rigid but demountable jig, and are then bound together by insulators which are viscous at the time of application but which later solidify into rigid insulating m'embersprior to removal of the jig; As' a resultof'this procedure the gun is in effect a rigid unitary assembly with the parts maintained in accaurate axial alignment and insulated effectively from one another. Accordingly, in the drawings, which show preferred embodiments of the methods and products:

Fig. 1 shows preliminary steps in assembling the gun according to the-invention. Fig. 2 represents succeeding stepsin the inventive method. i

Fig. 3 is a general plan view, partly in section, of a cathode-ray tube embodying thegun assembly of Fig. 2.

Fig. 4 is a sectional view of the gun of Fig. 2 taken along the lines 4-4 thereof.

Figs. 5 and 6 show successive steps in assembling amodified form of electron gun.

Fig. 7 shows the gun of Fig. 6 mounted inside a typical cathode-ray tube envelope.

A feature of the invention relates to a method of assembling the parts of an electron gun whereby axial symmetry is assured during each'step of the assembly, without requiring the use of preformed rigid spacer members such aseerarnic discs, rings or the like.

Another feature relates bling and axially aligning the parts of anelectron gun whereby the insulator fastening and spacing means are not applied until the parts have been previously mechanically aligned.

"A further feature relates to the method of fastening the parts of an electron-gun in axial alignment by using an insulator in a viscous state which, upon hardening, rigidly retains and insulates the parts from one another.

A still further feature rel tes to thenovel or-' ganizatlon, arrangement and'relative connection of parts which constitute a simple, cheap and highly accurate electron-gun assembly.

' Other features and advantages not specificallye'numerated will be apparent after a considerato a method of assem- Fig. 8 isa section of Fig. 2 taken. along the lines 88 thereof. Y

Fig. 9 is a cross-sectional viewof Fig. 6 taken along the line 9-9 thereof. 1

Referring to Fig. 2 of the drawings, the electron gun comprises in general an electron-emitting cathode in the form of a hollow metal sleeve I of nickel or other suitable metal, having its forward end closed by a metal cap 2, the outer flat surface of the cap beingprovided with a small spot of electron-emitting material of known composition. It will be understood that the emissivematerial is'arranged to be heated to electron-emitting temperature by a suitable heater (not shown), for example by a heater filament insulatingly mounted within sleeve I and capable of being heated in the manner well known in the art. For the purpose of controlling the intensity of the electron beam developed by the cathode,

alignment with apertures 4 and 6.

first anode 1. Thus in the tube as shownin Fig. 3, the second anode may consist of a C0317. ing 8 of aquadag or other conductive material applied to the inside surface cfthe bulb 9, this coating preferably extending intothe ne'ck H! of I Ordinarily a second anode is used in conjunction with the that no strains can be set up across the glass, consequently as the glass cools, it maintains its configuration with only a very slight shrinkage due to thermal expansion. After the three sets .of metal tabs have been thus united together by their respective glass beads, allthree beads are the bulb and terminating adjacent the forward end of anode 1 as shown, it being understood that an appropriate connecting wire issealed into the I wall 9 to connect with coating 8. I

It is obvious therefore, that if the beamis'to be" I properly focussed on the usuallmiuerescent 0681\- ing II on the flattened endoi 'tube'il; that the various electrodes described must be maintained in predetermined alignment. and their-relatively lateral and longitudinal positions :must'also-be maintained. For this purpose' 'flhexgrideiecticde 3, electrode and the first anode I are held in axial alignment with one another by four sets of metal tabs '-or"-wire's.1each set: comprising three tabs l2, l3, l4. While the drawingstshmv-four sets of tabs a greater-or less :numberwef setsmay he-employed. Tabs I2 are welded or'otherwise -fa'stened to the electrod'eefi; tabs Bare .=lik;ewise welded to the electrodefi Landtabs- M are welded to the'electrode :I. With the tabs-bf each :set disposed in alignment, rthey 93.19- held rigidly in .iplaee in the lprop'erwspaced :relationby means "of beads l5 of an insulating-material which can be applied in :the viscous state :but which upon cooling, :hardens to form-a rigidinsulating mass. :Forexample; these beads'mayt'be ot v g esscr;other similar material.

The gun may be assemble by employing digs 0f the type shownfin Figs. 1 and 2. The jig of Fig. l' comprises a bracket 'Ni -adapted try-support for horizontal adjustment, a cylindrical mandrel comprising theesectionsJl, .118. Section" I 1 is recessed at "its righthand end -to receive the endof the addusting screw 4 9 and the left hand end of section i=8 -is;pointed in "orderthat :it :may be seatedin :the opening in bracket arm 2 1. Before assembling the-jig sections, the anede 'his slipped over-the mandrel I1 until it strikesca suitable-stop (not-shown) The electrode '5 is then slipped over the reduced left hand end'M of section M until' it abuts "against the shoulder 23. Preferably-the section I1 is provided with an additional sheulder zd tp accommodate the tabs l3. A spacing washer preferably made in two separablehalves is placed against the electrode 5, whereupon the-electrode 3 is slipped over; the mandrel; end zz to abut against the washer fit The mandrel section 48 is theniplace'd in :position and the assembled d :in successive steps heated to the annealing temperature of the glass and are allowed to cool simultaneously. After (the heads have hardened, the screw I9 is released the parts ofthe jig as well as the washer sectional; can bewithdrawn.

:The next step is the assembly of the cathode. fil his step is "illustrated in Fig. 2 and requires a --braclrt l6 having its right hand-end provided with jawsil (Fig. 8), one of which is removable anduheld inyplaceby the screws 28. The jaws PM are adapted to surround and grip the anode I to Lholdthe latter firmly in place during the cathode assembly. The cathode assembly comprises the sleeve I. to which have been previously welded around the. :periphery thereofa set of wire or metal tabs-s28. While-the-drawings 7 united parts (Fig. lihav been ilamped iniplace by the jaws 2L the sleeve 4 :is slipped bye!" .the

end of the horizontally adiustable mandrel, -29

and the mandrel is adjusted etc the torward: end of cap 2 oflthe cathode into the :tproper spaced relation la -the iopening l. elf desired, the cylindrical wall-of electrode; maybe .provided with .a series of sight openings {not shown) sothat the position of cap- 2 mth respect towopening 4 may be ascertaineddutinglthe asalignment by-means of' the screw 4 9.

At this stageiof the-assembly the insulator '-facili-tat thebuilding =up of the dinal unitary :b'oad t5.up--At;thetemperature attained during "this cperatiomthe viscosity *of theglass is solow rnent longitudinally-of the -bea'ds l5 .'have not b'een applied although the tsembly. When the cathode sleeve Tl.,has' been adjusted to the proper position, the mandrel 219 isr-locked in position by-thescrew-3B. v I

Preferably the supports 28 i which may be of tungsten, nickel or other suitable. -.re'ractory metal "have been previously provided withlsmall glass beads "Likewise the projectingiends of the tabs -31 carried by electrode 3 have been.v .previously provided with smallsg'lass Lbea'ds, it 'being understood ithat theiparts areassembled so that the projecting ends=of tabs 28 are contiguous with thesprojectingends tor the associated tabs 73']. By using a small intense fiame, t helbea ds (on tabs -28 and the beads on the tabs.v 31 are caused to join. If necessary, 'thesresultant lbeadsffl vmay 'be "builtup by hcatingt-a-smalltpiece or glass cane .used-a a welding rod. lain the-case of the damnation 01 the beads P5,; allthei messes! are *brought to their annealing temperature and are allowed wto cool simultaneously, thereby holding cathode I in its prefixed withrespect to grid-3. Aiter the ibeadsiifimar .@hariieh'dfthe screw--30=-is loosened and immunoassay be with ra n 'since the a t 'gun a rrigid assembly, whereupon fthe arms-1 1 may be opened to releasethe gun from the jig,

The @unitary gun may bmmoimtediincthe neck 10 of the cathode ray -tube (Fist 3) 2m suitable: manner, ior example amethsmgfra limay be clamped "around vthe"anode .1. andflsiiitailile support wires=34 t hlisirin'g.jareI sup- ,ported the wires 35 IJ'nto of the tube. -It be midetstood l astes cathoflefraytubeds proiiidhti yanks-u able beam deflecting "means such. as an elec romagnet surrounding the"'neck OI"$heTtube adjacent 'the ens we I {fit also .be

understood that electrostatic deflecting means in combination with coordinate electromagnetic defleeting means may be employed. In those types of tubes where the second anode is in the form of a metal electrode rather than in the form of a coating such as the coating 8' (Fig. 3) a similar method of assembly may be employed. Thus there is shown in Fig. 6 an electron gun of the same structure as that shown in Fig. 2. In this embodiment however, there is provided a second anode 31 in the form of a metal cylinder of larger diameter than the first anode 1, and adapted to overlap the right hand end of said anode 1 as shown. Preferably also the forward end of electrode 31 i provided. with a cap 38 having a central opening 39 designed to be in axial alignment with the openings 4 and 6. The method of assembling and uniting the electrodes I, 3, and 1 is the same as that described in connection with the corresponding assembly of Fig. 2. However, the mandrel section I1 in this embodiment (Fig. 5) is provided with an enlarged portion 40 of the same diameter as the internal diameter of electrode 31, and this portion 40 is undercut as indicated by the numeral H to accommodate the end of anode 1 so as to allow the electrodes 1 and 31 to be positioned in overlapping relation on the mandrel. Electrode 31 is provided with a series of circumferentially spaced metal tabs 42 and likewise the anode 1 is provided with an equal number of circumferentially spaced metal tabs 43 so positioned that when the electrodes 1 and 31 are assembled on the mandrel as shown in Fig. 5, the corresponding tabs 42 and 43 have their ends in adjacent spaced relation whereupon these tabs may be rigidly united by means of glass beads 44 in the manner already described for the beads l5 and 32.

The manner of assembly of the remaining parts of the electron gun is fully described in connection with Figs. 1 and 2 and further description thereof at this point is not believed necessary. The electron gun of Fig. 6 may be supported on the press 45 of the cathode-ray tube by means of the support wires 46. Likewise if desired, a pair of horizontal electrostatic deflecting plates 41 may be insulatingly supported from the anode 31 and a coordinate set of vertical deflecting plates 48 may be insulatingly supported in the manner shown in detail in Fig. 9. The plates 41 may be spaced by a glass bead 49, and plates 48 may be spaced by a similar glass bead (not shown).

While certain specific materials, numbers and arrangement of electrodes and shapes thereof have been described, it will be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention. Thus one or more perforated diaphragms may be mounted transversely within electrode 1 each diaphragm opening being in alignment with openings 4 and 6. .It will also be understood that the invention is not limited to a gun employing the auxiliary electrode 5 and this electrode may be omitted if desired.

What I claim is:

1. A mount for electron gun devices comprising an apertured cup-shaped electrode, a plurality of supporting members equi-spaced and attached around a wall of said electrode, a metallic cylinder positioned axially within the cup-shaped electrode, and with the greater part of the length of said cylinder surrounded by the cup-shaped electrode; a plurality of individual links rigidly connecting said supporting members with said cylinder each of said links comprising a metal tab welded to the cylinder, a metal tab welded to the cup-shaped electrode with the ends of said tabs extending outwardly beyond said cup-shaped electrode and rigidly united by an individual vitreous bead; and a common stem upon which all said electrodes are supported as a unit.

2. A mount for electron gun devices, compris ing a cylindrical electrode planarly closed at one end, said end having an aperture for the passage of an electron stream, a cathode electrode within said cylindrical electrode and having its end in alignment with said aperture,

" means to support said cathode concentrically within said cylindrical electrode comprising a plurality of individual links each consisting of a metal tab fastened to the cathode and a metal tab fastened to the cylindrical electrode with the ends of the tabs extending beyond the ends of the cylindrical electrode and united by individual vitreous beads, a plurality of other electrodes having electron passage ways in alignment with said aperture, stud members aflixed to each of said other electrodes, supporting means engaging the studs and holding the electrodes in predetermined spaced relation, and a common stem upon which all the electrodes are supported as a unit.

ROBERT M. BOWIE. 

